Float analysis of non-serial repetitive activities

Floats and critical path(s) are important issues in construction management practice. In critical path method, activities not on the critical path(s) must have float. Float measures the amount of time an activity can be delayed before it becomes critical. Consecutive repetitive activities have production rates, which may vary considerably from one activity to another. This creates a different situation (from traditional non-repetitive activities) such that repetitive activities may have rate float, in addition to time float. In this paper, a proposed model for determining different types of floats for non-serial repetitive activities is developed. The traditional concept of time float is extended to repetitive activities. Rate float, which is an inherent property of repetitive activities, is also determined. Float analysis is performed in a very similar way to Critical Path Method (CPM) analysis, without the need for graphical aids. The analysis is based on a repetitive scheduling method, which utilizes a traditional CPM network of a typical unit, in which overlapping activities are used to model repetitive activities. A constant activity production rate is assumed and resource continuity is maintained. The method for determining time floats (total and free) and the rate float of non-critical activities and of non-controlling segments of controlling activities is described in detail. The proposed model was automated by a macro-program, which has been coded on a commercial scheduling software to facilitate float determination.